Percutaneous transluminal coronary angioplasty (PTCA) is widely used as the primary treatment modality in many patients with coronary artery disease. PTCA can relieve myocardial ischemia in patients with coronary artery disease by reducing lumen obstruction and improving coronary flow. The use of this surgical procedure has grown rapidly, with 39,000 procedures performed in 1983, nearly 150,000 in 1987, 200,000 in 1988, 250,000 in 1989, and over 500,000 PTCAs per year are estimated by 1994 (Popma et al., Amer. J. Med., 88: 16N-24N (1990); Fanelli et al, Amer. Heart Jour., 119: 357-368 (1990); Johnson et al., Circulation, 78 (Suppl. II): 11-82 (1988)). Stenosis following PTCA remains a significant problem, with from 25% to 35% of the patients developing restenosis within 1 to 3 months. Restenosis results in significant morbidity and mortality and frequently necessitates further interventions such as repeat angioplasty or coronary bypass surgery. As of 1993, no surgical intervention or post-surgical treatment has proven effective in preventing restenosis.
The processes responsible for stenosis after PTCA are not completely understood but may result from a complex interplay among several different biologic agents and pathways. Viewed in histological sections, restenotic lesions may have an overgrowth of smooth muscle cells in the intimal layers of the vessel (Johnson et al., Circulation 78 (Suppl. 11): II-82 (1988)). Several possible mechanisms for smooth muscle cell proliferation after PTCA have been suggested (Popma et al., Amer. J. Med., 88: 16N-24N (1990); Fanelli et al, Amer. Heart Jour., 119: 357-368 (1990); Liu et al., Circulation, 79: 1374-1387 (1989); Clowes et al., Circ. Res., 56: 139-145 (1985)).
Compounds that reportedly suppress smooth muscle proliferation in vitro (Liu et al., Circulation, 79: 1374-1387 (1989); Goldman et al., Atherosclerosis, 65: 215-225 (1987); Wolinsky et al., JACC, 15 (2): 475-481 (1990)) may have undesirable pharmacological side effects when used in vivo. Heparin is an example of one such compound, which reportedly inhibits smooth muscle cell proliferation in vitro but when used in vivo has the potential adverse side effect of inhibiting coagulation. Heparin peptides, while having reduced anti-coagulant activity, have the undesirable pharmacological property of having a short pharmacological half-life. Attempts have been made to solve such problems by using a double balloon catheter, i.e., for regional delivery of the therapeutic agent at the angioplasty site (e.g., Nabel et al., Science, 244: 1342-1344 (1989); U.S. Pat. No. 4,824,436), and by using biodegradable materials impregnated with a drug, i.e., to compensate for problems of short half-life (e.g., Middlebrook et al., Biochem. Pharm., 38 (18): 3101-3110 (1989); U.S. Pat. No. 4,929,602).
At least five considerations would, on their face, appear to preclude use of inhibitory drugs to prevent stenosis resulting from overgrowth of smooth muscle cells. First, inhibitory agents may have systemic toxicity that could create an unacceptable level of risk for patients with cardiovascular disease. Second, inhibitory agents might interfere with vascular wound healing following surgery and that could either delay healing or weaken the structure or elasticity of the newly healed vessel wall. Third, inhibitory agents which kill smooth muscle cells could damage surrounding endothelium and/or other medial smooth muscle cells. Dead and dying cells also release mitogenic agents that might stimulate additional smooth muscle cell proliferation and exacerbate stenosis. Fourth, delivery of therapeutically effective levels of an inhibitory agent may be problematic from several standpoints: namely, a) delivery of a large number of molecules into the intercellular spaces between smooth muscle cells may be necessary, i.e., to establish favorable conditions for allowing a therapeutically effective dose of molecules to cross the cell membrane; b) directing an inhibitory drug into the proper intracellular compartment, i.e., where its action is exerted, may be difficult to control; and, c) optimizing the association of the inhibitory drug with its intracellular target, e.g., a ribosome, while minimizing intercellular redistribution of the drug, e.g. to neighboring cells, may be difficult. Fifth, because smooth muscle cell proliferation takes place over several weeks it would appear a priori that the inhibitory drugs should also be administered over several weeks, perhaps continuously, to produce a beneficial effect.
As is apparent from the foregoing, many problems remain to be solved in the use of inhibitory drugs to effectively treat smooth muscle cell proliferation. Thus, there is a need for a method to inhibit or reduce stenosis due to proliferation of vascular smooth muscle cells following traumatic injury to vessels such as occurs during vascular surgery. There is also a need to deliver compounds to vascular smooth muscle cells which exert inhibitory effects over extended periods of time.
The present invention provides a therapeutic method comprising the administration of at least one therapeutic agent to a procedurally traumatized, e.g., by an angioplasty procedure, mammalian vessel. Preferably, the therapeutic agent is a cytoskeletal inhibitor. Preferred cytoskeletal inhibitors in the practice of the present invention, include, for example, taxol and analogs or derivatives thereof such as taxotere, or a cytochalasin, such as cytochalasin B, cytochalasin C, cytochalasin A, cytochalasin D, or analogs or derivatives thereof. The administration of a therapeutic agent of the invention is effective to biologically stent the vessel, inhibit or reduce vascular remodeling of the vessel, inhibit or reduce vascular smooth muscle cell proliferation, or any combination thereof. The administration of the therapeutic agent preferably is carried out during the procedure which traumatizes the vessel, e.g., during the angioplasty or other vascular surgical procedure. The invention also provides therapeutic compositions and dosage forms adapted for use in the present method, as well as kits containing them.
Thus, one embodiment of the invention provides a method for biologically stenting a traumatized mammalian blood vessel. The method comprises administering to the blood vessel an amount of a cytoskeletal inhibitor in a liquid vehicle effective to biologically stent the vessel. As used herein, xe2x80x9cbiological stentingxe2x80x9d means the fixation of the vascular lumen in a dilated state near its maximal systolic diameter, e.g., the diameter achieved following balloon dilation and maintained by systolic pressure. The method comprises the administration of an effective amount of a cytoskeletal inhibitor to the blood vessel. Preferably, the cytoskeletal inhibitor is dispersed in a pharmaceutically acceptable liquid carrier, e.g., about 0.1 to about 10 xcexcg for cytochalasin B/ml of aqueous vehicle, and preferably administered locally via a catheter. Another preferred embodiment of the invention is a cytochalasin or analog thereof dispersed in a pharmaceutically acceptable liquid carrier at about 0.001 to about 25 xcexcg per ml of aqueous vehicle. Preferably, a portion of the amount administered penetrates to at least about 6 to 9 cell layers of the inner tunica media of the vessel and so is effective to biologically stent the vessel.
Preferred catheter administration conditions include employing a catheter to deliver about 4 to about 25 ml of a composition comprising the cytoskeletal inhibitor dispersed or dissolved in a pharmaceutically acceptable liquid vehicle. The cytoskeletal inhibitor is delivered at a hub pressure of about 3 to about 8 atm, more preferably about 4 to about 5 atm, for about 0.5 to about 5 minutes, more preferably for about 0.7 to about 3 minutes. Preferred hydrostatic head pressures for catheter administration include about 0.3 to about 1.0 atm, more preferably about 0.5 to about 0.75 atm. The amount of therapeutic agent is controlled so as to allow vascular smooth muscle cells to continue to synthesize protein, which is required to repair minor cell trauma, and to secrete interstitial matrix, thereby facilitating the fixation of the vascular lumen preferably in a dilated state near its maximal systolic diameter, i.e., to provide a biological stent of the vessel. Preferably, the therapeutic agent is administered directly or substantially directly to the traumatized area of the vascular smooth muscle tissue.
The invention further provides a method for inhibiting or reducing vascular remodeling of a traumatized mammalian blood vessel, by administering an effective amount of a cytoskeletal inhibitor to the traumatized blood vessel.
As described hereinbelow, a dose response study showed that cytochalasin B had a two logarithmic therapeutic index (TI). A large therapeutic index allows the diffusion of therapeutic levels of the agent from the delivery system, e.g., an implantable device, without toxicity to cells immediately adjacent to the exit port of the system. Moreover, even at the maximum concentration of cytochalasin B in a liquid vehicle, there was little or no toxicity observed in cells adjacent to the delivery system. It was also found that cytochalasin B and taxol both inhibit intimal proliferation in vessels subjected to a procedural vascular trauma. This inhibition results in a more rapid and complete endothelialization of the vessel wall following the trauma.
The invention also provides a therapeutic method comprising inhibiting diminution of vessel lumen diameter by administering to a traumatized vessel of a mammal an effective amount of a cytoskeletal inhibitor. The cytoskeletal inhibitor is administered via an implantable device, wherein the implantable device is not a catheter which has a first and a second expansile member, i.e., balloons, which are disposed on opposite sides of the vessel area to be treated in order to isolate the portion of the vessel to be treated prior to cytoskeletal inhibitor administration. Preferably, the isolated portion of the vessel is not washed to remove blood prior to cytoskeletal inhibitor administration (xe2x80x9cbloodless angioplastyxe2x80x9d). xe2x80x9cIsolated,xe2x80x9d as used above, does not mean occlusive contact of the actual treatment area by the catheter balloon, which is preferred in the practice of the present invention. Moreover, bloodless angioplasty, such as that described in Slepian, U.S. Pat. No. 5,328,471, i.e., in which the region to be treated is washed, may introduce trauma or further trauma to the vessel, may increase the potential for complications and is not necessary to achieve a beneficial effect.
Thus, the invention further provides a method for inhibiting or reducing diminution in vessel lumen volume in a traumatized mammalian blood vessel. The method comprises administering to the blood vessel of a mammal an effective amount of cytoskeletal inhibitor, wherein the cytoskeletal inhibitor is in substantially crystalline form and wherein the crystals are of a size which results in sustained release of the cytoskeletal inhibitor. Preferably, the crystals are of a size of about 0.1 micron to about 10 mm, preferably about 1 micron to about 25 micron, in size. Methods to determine the size of crystals useful for sustained release are well known to the art. Preferably, the cytoskeletal inhibitor is administered in situ, by means of an implantable device, wherein the cytoskeletal inhibitor is releasably embedded in, coated on, or embedded in and coated on, the implantable device. Preferably, the crystalline cytoskeletal inhibitor is releasably embedded in, or dispersed in, a adventitial wrap, e.g., a silicone membrane. For example, a preferred therapeutic implantable device of the invention comprises about 5 to about 70, preferably about 7 to about 50, and more preferably about 10 to about 30, weight percent of a cytochalasin, e.g., cytochalasin B or an analog thereof, per weight percent of the adventitial wrap. Another preferred therapeutic implantable device of the invention comprises about 1 to about 70, preferably about 2 to about 50, and more preferably about 3 to about 10, weight percent of taxol or an analog thereof per weight percent of the adventitial wrap. Alternatively, a preferred therapeutic implantable device of the invention comprises about 35 to about 70, preferably about 35 to about 60, and more preferably about 35 to about 50, weight percent of taxol or an analog thereof per weight percent of the adventitial wrap.
Alternatively, the crystalline cytoskeletal inhibitor may be suspended in a vehicle which yields a solution comprising the crystals, i.e., it is a saturated solution.
The invention further provides a therapeutic method. The method comprises administering to a traumatized mammalian blood vessel a sustained release dosage form comprising microparticles or nanoparticles comprising a cytoskeletal inhibitor, e.g., cytochalasin, taxol, or analogs thereof. The sustained release dosage form comprising a cytochalasin or analog thereof is preferably administered via an implantable device which is not a catheter used to perform bloodless angioplasty. The amount administered is effective inhibit or reduce diminution in vessel lumen area of the mammalian blood vessel. The sustained release dosage form preferably comprises microparticles of 4 to about 50 microns in diameter. The sustained release dosage form can also preferably comprise about 2 to about 50, and more preferably greater than 3 and less than 10, microns in diameter. For nanoparticles, preferred sizes include about 10 to about 5000, more preferably about 20 to about 500, and more preferably about 50 to about 200, nanometers.
Also provided is a method comprising administering to a mammalian blood vessel a dosage form of a cytochalasin or an analog thereof in a non-liquid vehicle or matrix effective inhibit or reduce diminution in vessel lumen area of the mammalian blood vessel. Preferably the dosage form is a substantially solid dosage form. As used herein, xe2x80x9csolid formxe2x80x9d does not include microparticles, nanoparticles, and the like. The non-liquid vehicle or matrix preferably includes, but is not limited to, a gel, paste, or a membrane which comprises the cytochalasin or analog thereof.
Also provided is a kit comprising, preferably separately packaged, at least one implantable device adapted for the in situ delivery, preferably local delivery, of at least one cytoskeletal inhibitor to a site in the lumen of a traumatized mammalian vessel and at least one unit dosage form of the cytoskeletal inhibitor in a liquid vehicle adapted for delivery by said device. The administration of at least a portion of the unit dosage form to the traumatized vessel is effective to biologically stent the vessel, inhibit or reduce the vascular remodeling of the vessel, inhibit or reduce vascular smooth muscle cell proliferation, or any combination thereof.
Further provided is a kit comprising, preferably separately packaged, an implantable device adapted for the delivery of at least one therapeutic agent to a site in the lumen of a traumatized mammalian vessel and a unit dosage form comprising at least one cytoskeletal inhibitor, wherein the administration of at least a portion of the unit dosage form is effective to inhibit or reduce diminution in vessel lumen diameter of the vessel. The device is not a catheter which has a first and a second expansile member which are disposed on opposite sides of the region to be treated so as to isolate a portion of the vessel to be treated prior to administration or wherein the isolated portion of the vessel is not washed to remove blood prior to administration.
The invention also provides a kit comprising, separately packaged, an implantable device adapted for the delivery of at least one therapeutic agent to a site in the lumen of a traumatized mammalian vessel and a unit dosage form comprising an amount of microparticles or nanoparticles comprising taxol or an analog thereof. Preferably, the kit also comprises a second unit dosage form comprising a pharmaceutically acceptable liquid carrier vehicle for dispersing said microparticles or said nanoparticles prior to delivery. The delivery of the dispersed microparticles or nanoparticles to the traumatized mammalian vessel is effective to inhibit or reduce diminution in vessel lumen diameter in the vessel.
Yet another embodiment of the invention is a pharmaceutical composition suitable for administration by means of an implantable device. The composition comprises an amount of a cytochalasin or analog thereof effective to inhibit or reduce stenosis or restenosis of a mammalian vessel traumatized by a surgical procedure and a pharmaceutically acceptable non-liquid release matrix for said cytochalasin. Preferably, the release matrix comprises a gel, paste or membrane.
Also provided is a unit dosage form. The unit dosage form comprises a vial comprising about 10 to about 30 ml of about 0.001 xcexcg to about 25 xcexcg of a cytoskeletal inhibitor, preferably a cytochalasin, per ml of liquid vehicle, wherein the unit dosage form is adapted for delivery via an implantable device, and wherein the vial is labeled for use in treating or inhibiting stenosis or restenosis. Preferably, the unit dosage form comprises a vial comprising about 10 to about 30 ml of about 0.01 xcexcg to about 10 xcexcg of cytochalasin B per ml of liquid vehicle. Thus, the volume present in a vial may be greater than, or about the same as, the volume present in the implantable device. Likewise, the volume present in the implantable device may be greater than, or about the same as, the volume administered. Similarly, the volume administered may be greater than, or about the same as, the volume which has a beneficial effect.
Further provided is a unit dosage comprising a vial comprising a cytostatic amount of a cytoskeletal inhibitor in a pharmaceutically acceptable liquid vehicle. Preferably, the cytoskeletal inhibitor comprises a cytochalasin, taxol, or an analog thereof.
The invention also provides therapeutic devices. One embodiment of the invention comprises a therapeutic shunt comprising an amount of a cytoskeletal inhibitor effective to inhibit stenosis or reduce restenosis following placement of the therapeutic shunt. Another embodiment of the invention comprises therapeutic artificial graft comprising an amount of a cytochalasin or analog thereof to inhibit stenosis or reduce restenosis following placement of the graft. Yet another embodiment of the invention comprises a therapeutic adventitial wrap comprising an amount of a cytoskeletal inhibitor effective to inhibit stenosis or reduce restenosis following placement of the wrap.